AnaChem Module 1 PDF

PALAWAN STATE UNIVERSITY College of Sciences Chem 4/L – ANALYTICAL METHODS FOR BIOLOGY NATURE OF ANALYTICAL CHEMISTRY MODULE 1  Table of Contents Content...

PALAWAN STATE UNIVERSITY College of Sciences Chem 4/L – ANALYTICAL METHODS FOR BIOLOGY NATURE OF ANALYTICAL CHEMISTRY MODULE 1  Table of Contents Content Page Learning Outcomes.………………………………………………………......................... 2 Overview…….………………………..……………………………………………….......... 3 Initial Activity…………………….…………………………………………........................ 4 1.1 Introduction to Analytical Chemistry...…….......................................................... 5 Learning Check 1.1 …………………………. ……………………………………........ 7 1.2 Important Terms in Chemical Analysis.…………………………………………......... 8 Learning Check 1.2 ………………………………………………………………......... 10 1.3 Classes of Quantitative Analytical Methods……………………………………......... 11 Learning Check 1.3 ……………………………………………………....................... 13 1.4 Steps in a Typical Quantitative Analysis…............................................................ 14 Learning Enrichment ……………………….. ……………………………………....... 16 Learning Check 1.4………………………………………………………………......... 17 1.5 Relationship of Analytical Chemistry with other Branches of Science.………......... 18 2 Learning Check 1.5 ………………………………………………………………......... 21 Evaluation ……..………………………………..…........................................................ 22 Grading Rubric.......................................................................................................... 24 Reflection.................................................................................................................. 25 References…………………………………………........................................................ 26 Page 1  Learning Outcomes After going through in this module, you should be able to: 1. Give examples of qualitative analysis and quantitative analysis; 2. Describe briefly the important terms in chemical analysis; 3. Differentiate the various types of analytical methods; 4. Describe how each step of the typical quantitative analysis is done; 5. Cite examples of the role/ importance of chemical analysis in Biology and in other fields of sciences. 3 Page 2  Overview Welcome to Analytical Chemistry! In this module you will be introduced to the Science of Chemical Measurements: what is analytical chemistry, what different methods are used in determining and quantifying chemicals present in a given material, the important terms used in chemical analysis, what are the steps involved in quantitative chemical analysis, and the importance of analytical chemistry to your discipline and to other fields of sciences. YouTube links are also provided to facilitate your learning. At the end of this module, you will write a Reflection Paper on journal articles dealing with chemical analysis. You may study this module at your own pace but be sure to submit the requirements on the due date. For those who will be taking this course off line, please visit our Google classroom then view the announcements and other requirements for 4 submission. Page 3  Initial Activity I want to know if you have any idea/ knowledge about analytical chemistry. Please write something about this topic: Analytical Chemistry First, I know that ____________________________________________________________ __________________________________________________________________________ Secondly, I know that ________________________________________________________ __________________________________________________________________________ Finally, I know that __________________________________________________________ __________________________________________________________________________ 5 Page 4  Discussion 1.1 Introduction You accidentally found a small piece of rock glittering on the mountain side while you are hiking with your friends. You wanted to find out if it contains something valuable like gold, silver and other precious metals and if it does, how much? How will you know? Please study the following images and infer what they are trying to convey to you. What does each picture tell you? Figure 1.1. Analysts conducting chemical/ clinical analysis Sources: https://edu.rsc.org/experiments/titrating-sodium-hydroxide-with-hydrochloric- acid/697.article & https://radiusstaffingsolutions.com/how-laboratory-scientists-are-helping- 6 manage-coronavirus/ The pictures above show how chemical analysis is done. Chemical analysis is studied in Analytical chemistry. Page 5  Discussion Analytical chemistry is the qualitative and quantitative characterization of matter. Qualitative analysis deals with the identification of chemical compounds or elements present in a sample. Quantitative analysis deals with the measurement of the exact amount of compound or element present in a sample. For example, qualitative analysis might be able to determine the presence of lead in the paint on a toy while quantitative analysis detects how much concentration exists. Medical tests rely on quantitative analysis for information about a patient's health. 7 Page 6  Learning Check Learning Check 1.1 Use the table below to write examples of qualitative analysis and quantitative analysis. You may start with phrases like determination of ____________ in a _____________. Qualitative analysis Quantitative analysis 1 1 2 2 3 3 4 4 5 5 8 Page 7  Discussion 1.2 Important Terms in Chemical Analysis Before we proceed, please study the following terms used in chemical analysis. They will be useful in your understanding of the processes involved as you perform chemical analysis in the future. Sample – the material that is subjected to chemical analysis; contains the analyte. Example : seawater, an ore, a plasma, a powder Analyte - a substance to be measured in a given sample Ex. calcium in seawater, gold in an ore, antibodies in a plasma, amphetamine hydrochloride in a powder Matrix – everything else in the sample Interferences - other compounds in the sample matrix that interfere with the measurement of the analyte Example : Magnesium in seawater Homogeneous Sample - same chemical composition throughout Ex. steel, sugar water, juice with no pulp, alcoholic beverages Heterogeneous Sample - composition varies from region to region within the sample 9 Ex. raisin bread, soil, blood. Differences in composition may be visible or invisible to the human eye (most real samples are invisible) Analyze/Analysis - applied to the sample under study. Ex. We analyze water samples. Determine/Determination - applied to the measurement of the analyte in the sample. Ex. We determine calcium ion in water. Multiple Samples - Identically prepared from another source or from various sources Ex. water samples from different wells Replicate Samples - Splits of sample from the same source Page 8 Ex. water samples from one well  Discussion Calibration or standard curve - a graph showing detector response as a function of analyte concentration Standard solution - a solution containing known concentration of pure analyte Masking - the transformation of an interfering species into a form that is not detected Aliquot - small test portion of the sample Sampling - the process of selecting representative material to analyze Sample preparation - the series of steps needed to convert a representative bulk sample into a form suitable for chemical analysis 10 Page 9  Learning Check Learning Check 1.2 In your own words, explain briefly the following analytical terms and give one example for each: 1. Sample 2. Analyte 3. Matrix 4. Interference 5. Homogenous sample 6. Heterogenous sample 7. Multiple samples 8. Replicate samples 9. Aliquot 10. Sampling 11 Page 10  Discussion 1.3 Analytical Methods Now that you are already familiar with the common terms in chemical analysis, let me introduce you to the different methods used in the chemical analysis. There are two types of analytical methods used in the analysis of samples: 1. Classical methods - these are wet chemical methods such as precipitation, extraction, distillation, melting or boiling points, gravimetric and volumetric or titrimetric measurements (acid-base titration, oxidation-reduction titration, precipitation titration and complexometric titration). 2. Instrumental methods - analytical measurements (conductivity, electrode potential, light absorption or emission, mass to charge ratio, fluorescence, etc.) are made using instrumentation. Classes of Quantitative Analytical Methods Below are the different classes of quantitative analytical methods.  Gravimetric methods - determine the mass of the analyte or some compound chemically 12 related to it.  Volumetric methods - the volume of a solution containing sufficient reagent to react completely with the analyte is measured.  Spectroscopic methods - is based on the measurement of the interaction between electromagnetic radiation and analyte atoms or molecules.  Chromatographic methods - separation techniques and quantitation is based on calibration curve.  Electroanalytical methods - involve the measurement of electrical properties such as voltage, current, resistance and quantity of electrical charge. Page 11  Discussion  Miscellaneous Methods - include the measurement of such quantities as mass-to- charge ratio, rate of radioactive decay, heat of reaction, rate of reaction, sample thermal conductivity, optical activity, and refractive index Classification of Quantitative Method A. Based on Sample Size  Macro Analysis - used for sample mass more than 0.1 g.  Semimicro analysis - performed on a sample in the range of 0.01- 0.1 g  Micro analysis - sample mass ranges from 0.0001- 0.01g B. Based on Constituent Type  Major Constituent – ranges from 1%-100%  Minor Constituent - 0.01%-1% 13  Trace Constituent - 100 ppm - 1ppb  Ultra Trace Constituent – less than 1 ppb C. Based on Number of Constituent Analyzed  Complete Analysis - the quantities of all the constituents in the sample are determined.  Partial Analysis - quantity of only some constituents is determined.  Single Component Analysis - quantity of only one substance is determined. Page 12  Learning Check Learning Check 1.3 Differentiate the following: 1. Gravimetric method vs. volumetric method 2. Macro analysis vs. micro analysis 3. Major constituent vs. minor constituent 4. Trace constituent vs. ultra trace constituent 5. Complete analysis vs. partial analysis 14 Page 13  Discussion 1.4 Steps in a Typical Quantitative Analysis In conducting a quantitative analysis, the following steps should be followed: 1. Select a method The first step is the selection of a method. Will it be classical or instrumental? There are factors you must consider in choosing what method to use. These are:  Accuracy required  Cost of analysis  Number of samples to be analyzed  Time required for analysis  Skills required  Complexity of the sample  Number of components in the sample 2. Acquiring the Sample Sampling is the process of collecting a small mass of a material whose composition accurately represents the bulk of the material from which it was taken. To produce a valid and reliable result, an analysis must be performed on a representative sample. Sampling is the most difficult step in an analysis and a source of greatest error, thus proper sampling must be employed at all times. 3. Processing the Sample Sometimes no sample processing is required prior to the measurement step such as pH of the water sample which can be measured directly. Under most circumstances, samples need to be processed in a variety of ways. a) Preparing a Laboratory Sample Solid laboratory sample is ground to decrease particle size, mixed to ensure homogeneity, and stored for various lengths of time before analysis begins. Absorption or desorption of water may occur during each step. Since any loss or gain of water changes the chemical composition of solids, drying of samples should be done before the Page 14 analysis. The process is known as moisture content determination.  Discussion Liquid samples should be stoppered tightly to prevent evaporation or absorption of moisture which may change the composition of the analyte. If the analyte is a gas dissolved in a liquid, as in our blood gas sample, the sample container must be kept inside a second sealed container to prevent contamination by atmospheric gases. b) Defining Replicate Samples Most chemical analysis are performed on replicate samples. Replication improves the quality of the results and provides a measure of their reliability. Quantitative measurements on replicates are usually averaged and statistical test are performed on the result to establish their reliability. c) Preparing Solutions Most analysis are performed on solution of the sample with a suitable solvent. Ideally, the solvent must dissolve the entire sample including the analyte. The solid sample may require heating with aqueous solutions of strong acids, strong bases, oxidizing agents, reducing agents, or combination of such reagents. This is the most difficult and time-consuming task in the analytical process. 4. Eliminating Interferences Substances that interfere with a measurement must be eliminated. These are called interferences. Interference causes an error in the analysis by increasing or decreasing the quantity being measured. 16 5. Calibration and Measurement of Concentration An analytical result depends on the final measurement of a physical or chemical property (X). Ideally, the measurement of the property is directly proportional to the concentration (CA). CA = kX, where k is a proportionality constant. The process of determining the k is called calibration. 6. Calculating Results Analyte concentration from experimental data needs to be calculated. These computations are based on the raw experimental data collected in the measurement steps, the characteristics of the measurement instrument and the stoichiometry of the analytical reaction. 7. Evaluating Results by Estimating their Reliability Page 15 Analytical results are incomplete without an estimate of their reliability. Some measures of the uncertainties associated with computed results need to be provided.  Learning Enrichment For a detailed step by step procedure Illustrating the use of Analytical Chemistry to solve a problem, please read Feature 1.1 Deer Kill - A Case Study Illustrating the Use of Analytical Chemistry to Solve a Problem in Toxicology (Skoog et al. 2014, pp. 9-12). 17 Page 16  Learning Check Learning Check 1.4 Answer the following questions briefly. 1. Let us assume that you are working in an environmental laboratory as an analyst. What is the most important factor that you will consider in selecting a method to use? Why? ______________________________________________________________________ 2. What is a representative sample? ______________________________________________________________________ 3. Why is it that sampling is considered as the most difficult step in quantitative analysis? _______________________________________________________________________ 4. In chemical analysis, the more trials/ replicates the better. Why? ________________________________________________________________________ 18 5. In calculating results of quantitative analysis, why is it that the mean or average is reported? ________________________________________________________________________ Page 17  Discussion 1.5 Relationship of Analytical Chemistry with other Branches of Sciences Analytical chemistry is applied throughout industry, medicine, and all the sciences. It also plays a vital role in many research areas in chemistry, biochemistry, biology, geology, physics and other sciences. The interdisciplinary nature of chemical analysis makes it a vital tool in medical, industrial, government and academic laboratories throughout the world. 19 Figure 1.2. The relationship between analytical chemistry, other branches of chemistry and the other sciences (Skoog et al. 2014). Page 18  Discussion Roles of Analytical Chemistry 1. To establish economic value Analytical chemistry is used to determine the cost of a material or commodity. If the composition and quantities of a given material is known, then its economic value could be determined. 20  Quantitative determination of N in foods establishes their protein content and thus their nutritional value/ economic value.  Soil sample from ores with high % of Ni or Cu costs higher.  An 18 K gold is more expensive than a 10 K gold. 2. To Determine health hazards  Regular monitoring of water/air samples for possible pollution and contamination of heavy metals/microbes/ bacteria  Determination of toxic chemicals in imported foods, toys, etc.  Levels of H2S in the air are regularly monitored at CBNC  Sulfur dioxide concentration is regularly monitored in the crater of volcanoes which shows sign of eruption Page 19  Discussion 3. Diagnosing Disease  Concentration of O2 and CO2/glucose are determined in millions of blood samples.  Composition and quantities of substances in urine samples give a lot of information about one’s health condition.  Clinical/ medical laboratories conduct qualitative and quantitative analysis of the presence, absence, lack, or excess of certain chemicals in the body which signal certain diseases. 4. Quality Control  The mercaptan in household gas supplies is monitored continually to ensure it has a sufficient noxious odor to warn of dangerous leaks.  Quantities of HC, NO and CO present in automobile exhaust gases are measured to assess the effectiveness of smog-control devices. 5. Relating Properties to Composition and Structure  Material scientists rely heavily on quantitative analysis of crystalline germanium and silicon in their studies of semiconductor devices.  Analysis of steel during its production permits adjustments in its composition to achieve the desired strength, hardness, corrosion resistance, and ductility  Compare properties of gasoline with 93 octane rating with that of 87 octane rating. 21 6. Research  Almost all researches in the sciences and other related fields make use of analytical chemistry. Page 20  Learning Check Learning Check 1.5 As a science major student, what is the relationship of analytical chemistry with biology, or environmental science? Why are you required to take this subject/ course? __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ ___ 22 Page 21  References Skoog DA, West DM, Holler FJ and Crouch SR. 2014. Fundamentals of Analytical Chemistry. 9th ed. Brooks/ Cole. Singapore. Skoog DA, West DM, Holler FJ. 2012. Introduction to Analytical Chemistry. 8th ed. Cengage Learning, Asia, Pte. Ltd. YouTube Links How Do Analytical Chemists Help Our World? At https://www.youtube.com/watch?v=nhMN890_K2U Analytical Process at https://www.youtube.com/watch?v=Uyar8gzrDQY Analytical Process at https://www.youtube.com/watch?v=Uyar8gzrDQY&t=305s 23 Page 26